This invention relates generally to continuous cryogenic treatment of materials. More particularly, the invention relates to an apparatus and process for continuously feeding material, such as scrap, through a freezing zone to render it brittle so that, thereafter, it can be crushed or impacted and separated according to the various types of materials of which is it composed.
In the prior art, it is known to subject material, such as insulated wire, to a low temperature gas, such as nitrogen, in a liquid atomized state, so that the insulation becomes brittle and can be cracked off of the metallic wire, thereby separating the wire from the insulation. See, for example, U.S. Pat. No. 3,647,149. One disadvantage of the prior art devices, such as that shown in the referenced patent, wherein a conveyor belt is used in the freezing zone, is that it is difficult to lubricate the moving parts of the apparatus within the extremely cold environment. Also, there can be a frost build-up within the device and the accumulation of fine particles or other undesirable material.
Other problems that have arisen in prior art devices involve the distribution and agitation of the gas within the freezing chamber and, in particular, involve attempts to get maximum exposure of the product to the cooled gas and maximum utilization of the cooling effect of the gas.